Wall Thickness Data Collection

Report
Presented by
Doug Gapp
Pipeline Safety Planning Dept
Southwest Gas Corporation
August 19, 2014
Western Region Gas Conference


San Bruno Incident, September 9, 2010
Pipeline Hazardous Materials Safety
Administration (PHMSA) Advisory Bulletin ADB
11-01, Jan 10, 2011
 Evaluate risk – physical and operational characteristics

California Independent Review Panel San Bruno
(Recommendation 5.6.4.2), June 24, 2011
 Program to collect…construction and operating data

PHMSA 2011 Advanced Notice of Proposed
Rulemaking (Section D), August 25, 2011
 Requirements for collecting, validating, integrating and
reporting pipeline data

National Transportation Safety Board (NTSB),
August 30, 2011
 San Bruno 29 Recommendations
 Recommendations specific to Integrity Management
Program (IMP)
 Completeness/Accuracy Integrity Management Program Data

Federal legislation, January 3, 2012
 Confirm material strength
 Pipelines operating in high-consequence areas (HCAs)
 Greater than 30 % specified minimum yield strength (SMYS)

California Public Utilities Commission 17 Hazards
Report (Item 4), March 14, 2012
 Verifiable and traceable records

PHMSA
 Integrity Verification Process
 Likely will require action on transmission pipe
operating in HCAs and Class 3 and 4 locations

Focus of NTSB, federal legislators, regulatory
agencies
 Transmission pipelines
 HCAs
 Data – Know your pipelines so you can properly
evaluate risk


1979 Acquired
gas system
from Tucson
Gas and
Electric
1984 Acquired
gas system
from Arizona
Public Service

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
November 2012 proposed field data
collection initiative-wall thickness pilot
Goal: improve knowledge and records of
company pipeline characteristics
Specifically:
 Collect wall thickness data where not documented
 Accurately classify pipeline
 Appropriate integrity management application
 Transmission Integrity Management Program (TRIMP)
 Distribution Integrity Management Program (DIMP)
 pipe that meets transmission classification by actual
properties, not lack of records


Conventional In-line Inspection (ILI)
Other ILI tools
 Pipetel Explorer – Southern Nevada Division (SND)

Dig and inspects (D&Is)
 Southern Arizona Division (SAD)
•
•
Available for pipe sizes 6” to 36”
•
Wireless/battery operated
•
~ 3300 foot range
•
Camera (front and back)
•
Remote Field Eddy Current Sensor (RFEC)
•
Magnetic Flux Leakage (MFL)
•
Maneuver through standard fittings
Either live or de-gassed pipeline
Explorer Project
Las Vegas


Successful launch and recover robotic tool
(tetherless)
Into a non-live natural gas pipeline
 Obtain wall thickness (WT) data
 Identify potential metal loss

First SWG commercial application
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Crossing that prohibited conventional inline
inspection tools from passing
Pipeline diameter – 6-inch
Maximum operating pressure (MOP) – 125 psig
 5522 feet unconfirmed wall thickness (WT)
Conservative assumption of 0.083 inches WT
21 feet 0.156 inches WT
Specified Minimum Yield Strength (SMYS)
unknown
 Conservative assumption of 24,000 psi
 20.78% SMYS at MOP

Vintages
 1964, 1968, and 1972
• Originally planned for 3 bellholes, ended up with 4
• Tool run twice for each distance
• Wall thickness data
• Metal loss data
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Urban location traffic & noise
Night work
Crossing over storm drain
Question: What if it gets stuck?
Answer: Put a leash on the pig
Manual
Tether
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Pre excavate pits, larger than standard bellholes
Horizontal launch
Opted for out of service
Night work due to heat of summer
 Reduce project complexity
 Heat impacted equipment (no flow to cool)

Improvised air conditioning pipeline

Anomalies
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No Immediate or Scheduled repair required
No metal loss locations
7 suspected dents
3 suspected dents or material deposits
Wall Thickness data
 Majority of pipe is 0.156 inches (11.1% SMYS)
 some 0.188 inches WT (9.2% SMYS)
 Not the 0.083 inches WT
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Validate data – field work
Two locations for inspection
 Dent
 Lowest WT reading
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Updated WT attribute data
Final follow-up with vendor
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Experience with Explorer tool
Once confirmatory digs completed able to
correctly classify pipe
Avoided replacement
 Explorer cost between $200K-$300K per mile
 Compared to $2+ million/mile to replace

Questions on Explorer project?
Dig and
Inspect (D&I)
Project
Yuma
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Pipeline Diameter – 6-inch
Maximum Operating pressure – 150 psig
1.3 miles Unconfirmed wall thickness (WT)
 Conservative assumption of 0.083 inches
1.2 miles confirmed WT upstream classified as
transmission
Specified Minimum Yield Strength (SMYS)
unknown
 Conservative assumption of 24,000 psi
 24.9% SMYS

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7 HCAs
Vintages
 1954, 1955
• 35 D&I Bellholes
• Wall thickness data
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
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1954 vintage changed to 0.250 wall – 8.3%
SMYS
1955 vintage changed to 0.188 wall – 11.0%
SMYS
Cost Comparison
 Actual cost was approximately $50K
 Allowed reclassification 2.5 miles of pipe to highpressure distribution
 Lowered comparative risk

Southern Arizona Division D&I:
 Yuma-Wellton
 Approximately 93,000 feet of 4-inch pipe unknown
WT
 2 HCAs

Central Arizona Division Explorer ILI:
 Litchfield Ave
 Approximately 2500 feet of 6-inch pipe unknown
WT
 Almost entirely in an HCA
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Pipe with:
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Unknown wall thickness?
Operating at high % SMYS?
Actual wall thickness likely higher?
Unpiggable?
Determining actual wall thickness:
 Lowers relative risk in HCAs
 Accurately classify pipe
 Appropriate integrity management application

Questions???

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